Mentalizing - the ability to understand oneself and others by inferring mental states that lie behind overt behaviour - develops within the context of attachment relationships. It is crucial to self-regulation and constructive, intimate relationships, both of which are impaired in personality disorders because of sensitivity to losing mentalizing at times of anxiety and attachment stress. Loss of mentalizing leads to interpersonal and social problems, emotional variability, impulsivity, self-destructive behaviours, and violence. This practical guide on mentalization-based treatment (MBT) of personality disorders outlines the mentalizing model of borderline and antisocial personality disorders and how it translates into clinical treatment. The book, divided into four parts - the mentalizing framework, basic mentalizing practice, mentalizing and groups, and mentalizing systems - covers the aims and structure of treatment, outlines how patients are introduced to the mentalizing model so that their personality disorder makes sense to them, explains why certain interventions are recommended and others are discouraged, and systematically describes the process of treatment in both group and individual therapy to support more stable mentalizing. People with personality disorders commonly have comorbid mental health problems, such as depression and eating disorders, which complicate clinical treatment. Therefore, the book advises the clinician on how to manage comorbidity in treatment. In addition, mentalizing problems in families and social systems, for example, schools and mental health services are also covered. A families and carers training and support guide is provided as families and others are often neglected during the treatment of people with personality disorder. The book is a valuable guide for all mental health workers on how to effectively treat personality disorders. 1. The mentalizing framework 1. What is mentalizing? 2. Using the mentalizing model to understand personality disorder 3. Comorbidity 4. Assessment of mentalizing Fonagy 2. Mentalizing practice 5. Structure of mentalization-based treatment 6. Clinician stance 7. Principles for the mentalizing clinician 8. The mentalizing focus: support, empathy and validation 9. The mentalizing focus: clarification, affect elaboration, affect focus and challenge 10. Relational focus of mentalizing: transference tracers and mentalizing the relationship 3. Mentalizing groups 11. MBT-Introductory group (MBT-I) 12. Mentalizing group therapy 13. Antisocial personality disorder: mentalizing, MBT-G and common clinical problems 4. Mentalizing systems 14. Mentalizing and families: the Families and Carers Training and Support programme (FACTS) 15. Mentalizing the system Anthony Bateman is Expert member of National Institute for Clinical Excellence (NICE) development group for treatment guidelines for Borderline Personality Disorder in UK. He is currently Chair of the National Guideline Development Group for Eating Disorders. NHS clinical services are recognised by NHS England as a national demonstration site for the treatment of personality disorder. President of the European Society for the Study of Personality Disorders (ESSPD) from 2012-2015. He has authored 14 books and over 120 peer reviewed research articles on personality disorder and the use of psychotherapy in psychiatric practice. Received a senior scientist award from British and Irish group for the Study of Personality Disorder in 2012 and in 2015 the annual award for "Achievement in the Field of Severe Personality Disorders" from the BPDRC in the USA. Peter Fonagy, OBE, FMedSci, FBA, PhD, is Head of the Research Department of Clinical, Educational and Health Psychology and Freud Memorial Professor of Psychoanalysis at University College London. He is also CEO of the Anna Freud Centre in London and a Senior Investigator of the British National Institute for Health Research. Professor Fonagy is the recipient of numerous prizes, awards and other honours in the United Kingdom, the United States and internationally. He has published 17 books, over 400 original papers, and nearly 250 book chapters